PROJECT SUMMARY/ABSTRACT Adrenal adenomas affect 5%-10% of the population, discovered annually in about 4 million adults in United States. Patients with adrenal adenomas demonstrate an abnormal steroid secretion and metabolism, the most prevalent being called ?subclinical? mild, autonomous cortisol secretion (MACS). Available limited evidence suggests that patients with MACS suffer from very high-rates of vertebral fractures, many times not correlated with deterioration of bone density. Understanding how MACS affects bone metabolism and leads to fractures is significantly limited by heterogeneous patient populations and the multifactorial etiology of bone disease. The overall objective of the proposed project is to understand the epidemiology of fractures in patients with adrenal tumors and MACS, and to identify the elements of abnormal steroid secretion and metabolism that predict bone disease, and ultimately fractures. This will be accomplished in three specific aims. In Aim 1, the Olmsted county population will be accessed through the Rochester Epidemiology Project (REP) to determine the prevalence and incidence of fragility fractures in patients with adrenal tumors overall, and the effect of MACS severity on fragility on fracture occurrence will be established. The experiments proposed in Aim 2 will determine if the abnormal steroid metabolome observed in patients with MACS is associated with impaired bone density, quality, structure and metabolism that, in turn, are associated with an increased risk of both vertebral and non-vertebral fractures. The experiments proposed in Aim 3 will determine if the abnormal circadian pattern of cortisol secretion in patients with MACS is associated with abnormal calcium metabolism and alterations in bone turnover markers. The proposed career development award and associated candidate training address an important health problem of skeletal health in patients with MACS and prepare the candidate for an independent career in research, meeting the goal of the NIH mentored Patient-Oriented Research Career Development Award (Parent K23 - Independent Clinical Trial Not Allowed), PA-18-375. The exceptional resources and institutional support at Mayo Clinic, outstanding multi-disciplinary mentorship team, and proposed career development activities will allow the candidate to achieve her long-term goal of becoming an independent investigator and nationally recognized expert on steroid effects on bone health and design interventions that are effective in improving skeletal health of patients with adrenal tumors.